Let’s say I create a repeater field which includes an image field. Let’s say I then go and add a large number of rows, each with an image.
When ACF fetches the field, both in the backend and frontend, it loops through each row and independent calls wp_get_attachment_image and related functions to fetch and display the image.
This results in one SQL query for every single image, and becomes very slow very quickly.
I managed to work around this on the frontend by only storing image IDs, and adding this to the start:
$ids = array();
foreach ($field as $next) $ids[] = $next['image'];
$results = get_posts(array('post_type'=>'attachment','numberposts'=>-1,'post__in'=>$ids));
This get_posts call queries every image at all once, and caches all of the results in memory – so that any future get_post or wp_get_attachment_image call can look up the data immediately and doesn’t require further database access. The performance improvement is very noticable.
Would it be possible to add this type of call somewhere in the core code so that a) it would work when displaying the fields in the backend, and b) it would work if you another return value (eg image objects)?
